I’m a user of Booking.com, and I can say that they use a lot of “psychological” tricks to make me book a hotel. For example :
- Showing a lever meter of how crowded of a city : “Hotels in Porto is 95% booked at these dates”.
- Showing price info : “Price goes up this week, don’t miss your opportunity.”
- Showing info of viewers quantity : “5 people is looking at this hotel now.”
- Showing info of last booking : “Last booking 33 minutes ago.”
- Showing info that hotel rooms would be gone soon : “1 room left” with red colour text.
- Always giving the impression that they offer you a special discounted price.
I suppose they have a top notch of UX Designers and UX Writers ;)